This invention relates to locomotives and, more particularly, to a portable apparatus for testing operability of a locomotive from an external location.
Present day locomotives are complex machines having myriad electronic circuits and on-board computer systems. In a typical diesel-electric locomotive, a diesel engine runs at constant speed to drive an alternator supplying electric power to propulsion motors and to drive another alternator supplying alternating current (AC) electric power at a constant frequency for various appliances on the locomotive or in cars pulled by the locomotive. Each of these power systems require separate control systems for regulating locomotive speed or horsepower and for allocating a division of power between the power systems in accordance with the power available from the engine.
In addition to the complexity inherent in the control systems, locomotives are also designed to operate in multiple unit consists, thus increasing complexity. For example, when operating in a consist, operator commands in a lead locomotive must be transmitted to equivalent commands in a trailing locomotive. Accordingly, each locomotive circuit is not only responsive to on-board command functions but also to command functions from another interconnected locomotive.
Command functions are transmitted between locomotives via a hardwired cable typically referred to as a train line, each end of which terminates in a multiple unit (MU) connector and a governor connector. The MU connector passes the majority of functions between locomotives, such as an engine start command and motor excitation commands. The governor connector transmits only the functions associated with engine horsepower or locomotive speed. A particular excitation command issued on the MU connector may be acknowledged by a speed setting passed on the governor connector.
Historically, locomotive operability has been tested by individually checking each conductor in the train line and in the power and control compartments and by operating the locomotive and confirming that the locomotive responds to operator commands. A typical train line check would require a technician at each end of the locomotive, one of whom would apply a voltage to a particular conductor in the train line while the other confirmed that such voltage appeared at the opposite end of the train line, i.e., at the other MU connector.